This invention provides a reliable sensor that combines the useful features of presently available related devices upon the market, but does so in a manner that substantially eliminates the inaccuracy generated by inferior features normally used in currently available devices. More specifically, the current invention utilizes a microprocessor based electronic circuitry, that is designed to record the size, intensity, and nature of the precipitation involved, and being encountered.
Generally, sensing devices currently available in the field of weather observation and monitoring all share one or more characteristics, and as a result, suffer in deficiencies or inaccuracies of detection, due to the effects of environmental conditions. Most of the currently available devices are contact devices, which suffer mechanical problems caused by the environment and the impurities generated and currently prevailing within the environment, at the time of gauging. Some of these earlier devices utilize destructive means to distinguish between the liquid and solid, such as whether water or ice precipitation is being gauged, and as to whether or not precipitation is in the liquid stage, or is generated through heat, evaporation, or artificial refrigeration. Many of these earlier devices utilize electrical properties in the category of resistance, capacitance, or inductance, to provide for their generation of a charge that is supposed to be detective of the type of environment being monitored. But, many of these devices have generally proven unreliable, due to many circumstances, but primarily due to the pollutants that exist in the atmosphere, which can cause changes in the electrical properties of the sensing means, depending upon the environmental conditions existing for that moment. Devices which employ any of the mechanical or electromechanical components normally used, have likewise proven to be generally unreliable, due to the elements of weather itself, and that is whether the environment is currently composed of wind, temperature, humidity, and atmospheric pressure, or their rapidly changing conditions. Lightning and elements of pollution also add to inaccuracy in the operations of the conventional monitoring devices.
Conventional instruments for monitoring atmospheric phenomenon use a number of different approaches. For example, various types of instruments are available that detect rain, mist, snow, snow flurries, frozen rain, and fog. Haze, dust and smoke are some of the other phenomenon in the atmosphere which can effect the efficient monitoring of these current type meteorlogical instruments.
One instrument available measures the rate and volume of liquid precipitation, and is known as the tipping bucket concept, which utilizes two reservoirs of known volume to collect the liquid precipitation, in its liquid state, and then have reporting intervals for monitoring when light or intermittent precipitation occurs. But, when wind effects come into play, the tipping bucket instrument may understate the actual rate and volume of the precipitation being generated by the atmosphere.
Another device for measuring volume of liquid precipitation employs the use of a collection chamber. This collection chamber empties itself via an orifice at the bottom of the chamber. The orifice causes water to form droplets which are theoretically of the same size, and are counted by optical or electrical means. Errors in volume reported can be caused by foreign matter intefering with the orifice, or having some effect upon the viscosity of the liquid involved.
Another device which employs the use of a conductive grid is used to indicate the pressence of a liquid precipitation. Corrosive elements in the atmosphere acting upon the exposed metal components of the conductance grid causes electrolysis which eventually deteriorates the grid or its electrical connections. This can lead towards deficient results.
A laser weather identifyer (LWI) is another means for sensing precipitation, and utilizing optical technology. The light source of the LWI consists of a gas filled HeNe laser modulated at a particular frequency. The receiver consists of three individually mounted optical detectors. All three of these optical detectors measure the amount of change of light present in their respective fields of view. Two of the detectors are mounted off-axis of the transmitted light source. The purpose of these two off-axis detectors is to detect forward scatter light difused as a result of a particle of precipitation passing through the sample volume. The LWI unit has several deficiencies inherent primarily due to the type of technology utilized in its design. False alarms due to vibration caused by strong winds or aircraft or automotive activity in the area affected can deplete the reliability of results obtained from this device. Strong vibrations induced into the instrument can cause a false signal to be indicated due to movement of the transmitter and receiver in different directions. This results in a change in the amount of light received by the detector. Furthermore, changes in ambient light can cause false readings. Direct or reflective light from any source radiation on the detector or detectors results in a change in the amount of apparent light measured from the light transmitter. Errors caused by multiple particles in the sample volume simultaneously can cause improper readings. When two or more particles are present in the sample volume simultaneously, the amount of light detected by the receiver is reduced, thus presenting an indication of particle size larger than the actual size of the individual particles present. The aforementioned multiple particles can effect the indicated velocity of the weather being detected. When two or more particles enter and leave the beam in succession there will likely be an indication that a single particle is moving at a slower velocity than it actually is.
High energy requirements, due to the use of an inert gas filled laser and the excessive quantity of parts in the integrated circuits to incorporate three receivers limits the possibility of mounting at remote sights. It is difficult to maintain four optical instruments in precise alignment in any harsh environment of the atmostphere, to provide satisfactory results from an LWI type of instrument. The physical size of the LWI unit, once again, limits the possible sights to which it can be mounted and used, primarily due to lack of available space. Meteorlogical stations are usually located in remote areas, employing tripods or towers. The large size of the LWI unit limits its usage on these types of supporting members. The mounting of a large instrument must be structurally sound due to the increased amount of wind resistance. Furthermore, some times this will dictate that the instrument be mounted at ground level, thereby reducing its sensitivity, and accuracy, in providing the type of concise readings required. Large, high visible instruments and remote locations are also likely to be targets of vandalism.
Earlier sensors that rely on changes and amplitude of light at the detector source are susceptible to accumulation of foreign matter upon the lenses, which can likewise cause errors in readings.
An example of earlier patented instruments utilized for weather observing is shown in the United States patent to Hansen, et al, U.S. Pat. No. 4,613,938, and entitled "Present Weather Observing System Utilizing Particulate Size and Velocity Measurements." This device provides a beam radiation in the atmosphere, including means having a field of view intersecting said beam to define a sample volume, for use for detecting scattered radiation from particles within the sample volume. From that, the size and velocity of at least one particle precipitating through the sample volume can be determined.
The United States patent to Chadwick, U.S. Pat. No. 3,487,684, is upon a precipitation measurement gauge. This particular measurement device is for use for monitoring the degree of precipitation in isolated areas. The device includes a precipitation-receiving vessel, a hydraulic-pressure responsive means connected to the vessel to respond to changes in the hydraulic pressure of precipitation received by the vessel, and a signaling means connected to the pressure responsive means. In its defined preferred form, a magnetic core is utilized, carried by a hydraulic bellows, that moves in and out of a stationary electric coil in proportion to the hydraulic pressure of the precipitation received by the vessel. Means are included to provide in circuit form having a coil to record or transmit signals in accordance with the position of the core in the coil.